Hydraulic system for an installation for heating and generating domestic hot water

ABSTRACT

Hydraulic system comprising a three-way valve, the three-way valve comprising a first port for the connection to a primary heat exchanger through the circulation pump, a second port and a third port for connection to the heating circuit and to a secondary heat exchanger, respectively. The three-way valve is switchable between two positions in which the first port is in fluid communication with the second port or with the third port. The three-way valve is responsive to the pressure applied by a circulation pump, and has a displaceable obstructing member that may be moved due to transitions between an off-state and an on-state of the circulation pump. The obstructing member comprises a pair of sealing surfaces facing away from each other and suitable to engage reciprocatingly respective opposed seats of the three-way valve.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention concerns in general hydraulic systems that are arranged to distribute the water flows between different circuits of a system, particularly in installations for heating and generating domestic hot water.

Background

It is known that, in the aforesaid installations, motorized three-way valves are used to selectively direct water to various heat exchangers through different hydraulic circuits.

New solutions have recently been proposed that provide for the use of non-motorized three-way valves, which switch between different positions according to the pressure produced by the circulation pump.

An object of the present invention is to make available a hydraulic system for diverting a flow of water from a primary exchanger to a secondary exchanger or heating circuit that operates without a motor, and therefore does not require electrical energy to drive it but rather is driven only by the hydraulic energy of the water flow, which is simple and reliable.

SUMMARY OF THE INVENTION

This and other objects are achieved according to the invention with a hydraulic system for an installation for heating and generating domestic hot water, which heating installation comprises a primary heat exchanger for heating a water flow usable in a heating hydraulic circuit, a secondary heat exchanger for transferring heat from a water flow coming from the primary heat exchanger to a domestic water flow and a circulation pump for generating the water flow in the primary heat exchanger;

-   -   the hydraulic system comprising a three-way valve, said         three-way valve comprising a first port for connection to the         primary heat exchanger, a second port and a third port for         connection to the heating circuit and to the secondary heat         exchanger, respectively;     -   wherein said three-way valve is switchable between at least two         positions in which the first port is selectively in fluid         communication with the second port or with the third port;     -   wherein said three-way valve comprises a movable support and an         obstructing member carried by said movable support, at least one         of which is responsive to the pressure applied by the         circulation pump at the first port, at least one of said movable         support and obstructing member being movable due to transitions         between an off-state and an on-state of the circulation pump;     -   wherein the hydraulic system is characterized in that the         obstructing member is made up of a single sealing element (or         diaphragm) comprising a pair of sealing surfaces facing away         from each other and capable of engaging reciprocatingly the         respective opposed seats of the three-way valve, interposed         between the first and second port, and between the first and         third port, respectively.

According to the present invention it is therefore possible to direct the water into the different circuits of the heating system with a simple and reliable hydraulic system, which operates without a motor and therefore does not require electricity for its operation, being driven only by the hydraulic energy of the water flow.

With such a system the cost of the valve and the cost of the electrical/electronic control part of the valve are further reduced. Hydraulic performance is also improved and water hammering is avoided.

According to an embodiment, the three-way valve further comprises return means associated with the movable support, which produce an elastic force to bias the movable support towards an intermediate position between the opposed seats of the three-way valve, wherein this intermediate position is associated with the off-state of the circulation pump.

In particular, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said movable support is movable towards said seat against the action of said elastic force due to pressure when the circulation pump switches from the off-state to the on-state.

Moreover, said movable support may be capable of driving the obstructing member from one to the other of said opposed seats of the three-way valve due to said elastic force when the circulation pump switches from the on-state to the off-state.

According to a specific embodiment, the movable support is arranged to be slidable between the opposed seats of the three-way valve and the obstructing member is made as a flexible conical ring arranged around the movable support.

In this case, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said obstructing member is capable of overturning due to pressure when the circulation pump switches from the off-state to the on-state, as well as driving said movable support towards said seat against the action of said elastic force.

According to another specific embodiment, the movable support is arranged to be slidable between the opposed seats of the three-way valve, and the obstructing member is made as a ring arranged around the movable support and slidable with respect thereto.

In this case, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said movable support is capable of moving due to pressure toward said seat and with respect to the obstructing member, against the action of said elastic force when the circulation pump switches from the off-state to the on-state.

According to another specific embodiment, the obstructing member is carried by a S-shaped leaf axially biased to flex reciprocatingly towards one or the other of said opposed seats of the three-way valve, the obstructing member being formed as a bend of said leaf

In this case, the obstructing member is capable of reversing curvature and engaging one of said opposed seats of the three-way valve due to pressure when the circulation pump switches from the off-state to the on-state, and wherein the S-shaped leaf is capable of bringing the obstructing member into an intermediate position between said opposed seats, due to an elastic force produced by the leaf when the circulation pump switches from the on-state to the off-state.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparent from the detailed description that follows, provided by way of non-limiting example with reference to the accompanying drawings, wherein:

FIGS. 1a to 1c are partial schematic representations of different embodiments of an installation for heating and generating domestic hot water;

FIGS. 2-5 are cross-sectional views of a three-way valve according to the invention, in four different phases of an operating cycle;

FIGS. 6a and 6c-6e are cross-sectional views of a second embodiment of the three-way valve, in four different phases of an operating cycle; FIG. 6b is a perspective view of a movable support or shuttle of the three-way valve in FIGS. 6a and 6c -6 e;

FIG. 7 is a cross-sectional view of a variant of the three-way valve of FIG. 6 a;

FIG. 8 is a perspective view of a movable support or shuttle of the three-way valve in FIG. 7;

FIGS. 9 and 10 are cross-sectional views of further variants of the three-way valve in FIG. 7;

FIGS. 11 and 12 are cross-sectional views of a further variant of the three-way valve in FIG. 7, in two different operating positions;

FIG. 13 is a cutaway view of the three-way valve in FIGS. 11 and 12;

FIGS. 14 to 16 are cross-sectional views of a further variant of the three-way valve in FIG. 7, in a non-operating position and two different operating positions;

FIGS. 17a and 17b are simplified perspective views of another embodiment of the three-way valve.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a of the attached drawings schematically shows a heating appliance B of a type known per se, in particular a boiler, which comprises a hydraulic diversion system indicated collectively at A. In the following, reference will be made for convenience to a boiler, but it is understood that the invention may find application in any of the heating appliances normally used in installations for heating and generating domestic hot water.

The system A is connected between an outlet fitting 23 of the boiler and a primary heat exchanger 21 intended to heat a flow of water for use in a hydraulic heating circuit comprising (for example) a pipeline 22 extending between the outlet fitting 23 and an inlet fitting 20 of the boiler, and along which are interposed one or more radiators 24. The boiler B further comprises a secondary heat exchanger 25, to transfer heat from a flow of water coming from the primary heat exchanger 21 and flowing in a pipe 26, to a flow of domestic water flowing in a pipeline 27 extending between two fittings 28, 29 of the boiler. The fitting 28 is intended to be connected to a water source, e.g. to the water supply network, and the fitting 29 may be connected to a tap 30 for domestic hot water. In some embodiments the boiler B does not comprise the secondary heat exchanger 25 which is arranged outside the boiler itself, but is connected to the primary heat exchanger 21 and to the hydraulic system A in a similar way as shown in FIG. 1 b. The diagram shown in FIG. 1b may also be representative of the arrangement of the elements inside a boiler.

In the embodiment in FIGS. 1a and 1 c, the hydraulic system A comprises a circulation pump 7 and a three-way valve 8 arranged hydraulically in series and assembled in a single body. According to different embodiments, the pump 7 may be arranged both upstream and downstream of the three-way valve 8 with respect to the flow of the fluid that passes through the pump 7. According to different embodiments, the pump 7 may be arranged and/or both upstream and downstream of the primary heat exchanger 21 with respect to the flow of the fluid that passes through the pump 7. According to different embodiments, the hydraulic system A does not necessarily integrate the pump 7 in a single body (FIG. 1b ); this pump 7 is however present inside the heating installation.

The three-way valve 8 comprises, in FIG. 1, a first port 2, in the example a fluid inlet port, for connecting to the primary heat exchanger 21, a second port 3, in the example an outlet port, for connecting to the heating circuit 22, 24 through the fitting 23, and a third port 4, in the example a second outlet port, for connecting to the secondary heat exchanger 25.

With reference to FIG. 1 b, another embodiment of the heating and domestic hot water system is shown, in which there is no provision for a boiler as a stand-alone unit that encloses the individual components described above. In the embodiment shown in FIG. 1 b, elements corresponding to the preceding embodiment have been assigned the same numerical references. As may be seen in FIG. 1 b, the circulation pump 7 is arranged on the inlet side of the primary exchanger 21. In general, the primary exchanger 21 may, for example, be associated in a completely conventional way with a gas, wood or pellet burner, a heat pump, a solar cell, a district heating circuit.

With reference to FIG. 1 c, another embodiment of the installation for heating and domestic hot water is represented, in which the hydraulic system A is arranged on the inlet branch of the boiler B. In the embodiment shown in FIG. 1 c, elements corresponding to the embodiment in FIG. 1a have been assigned the same numerical references. In this case, the order of arrangement of the circulation pump and three-way valve is reversed with respect to FIG. 1 a, and the three-way valve would have two inlets (second and third port) and one outlet (first port), with the circulation pump arranged in series with the outlet of the three-way valve.

The structure and operation of different embodiments of the three-way valve 8 shall now be described.

The three-way valve 8 is switchable between at least two positions in which the first port 2 is selectively in fluid communication with the second port 3 or with the third port 4, so that the water passing through the primary exchanger 21 is directed to the heating circuit 22, 24 or to the secondary exchanger 25 for heating the domestic water.

The three-way valve 8 is of the non-motorized type, and is responsive to the pressure applied by the circulation pump 7 at the first port 2 (inlet port, in the example in FIG. 1a or 1 b, or outlet port, in the example in FIG. 1c ), as will be clarified hereinafter.

In this regard, reference is made to a first embodiment of the three-way valve, represented in FIGS. 2 to 5.

This three-way valve 8 comprises a valve body 81, in which are obtained the first port (inlet port) 2, the second port (first outlet port) 3 and the third port (second outlet port) 4, all of which are connected to a switching chamber 82 obtained in the valve body 81.

Inside the switching chamber 82 there is arranged an obstructing member 83 that takes the form of a flexible conical ring, which in turn is carried by a movable support 84 made as a sliding shuttle inside the valve body 81. The obstructing member 83 is made of a disc of flexible material (e.g. rubber) with a hole in the center, which, as a result of the difference in diameter between the hole of the disc and the larger diameter shaft of the movable support 84 on which it is mounted, assumes the shape of a flexible conical ring that is seen in FIG. 2. The direction of translation of the movable support is represented by the arrow x in FIG. 2. The obstructing member 83 has a first and second sealing surface 83 b and 83 c facing away from each other (i.e. facing in opposite and divergent directions), with respect to the direction of translation x of the movable support 84. The obstructing member 83 is mounted in a groove 84 a obtained in the movable support 84, in such a way that the obstructing member 83 is integral in translation with the movable support 84. The configuration of the groove 84 a is such as to allow the overturning of the obstructing member 83 (rotation at the point of contact with the movable support 84), i.e. the reversal of the taper direction with respect to the direction of translation x of the movable support 84, as will be clarified hereinafter.

At opposite ends, the movable support 84 is attached to guided rods 84 b and 84 c, which are inserted in corresponding guide holes 81 b and 81 c obtained in the valve body 81.

Between the ends of the movable support 84 and the respective counterparts of the valve body 81 are interposed respective opposed elastic means 85 b and 85 c, which bias the movable support 84 towards an intermediate position or equilibrium position, represented in FIGS. 2 and 4, which occurs when the same pressure is applied in ports 2, 3 and 4 (i.e. circulation pump 7 switched off). In the example shown, the elastic means 85 b and 85 c are made as coil springs arranged coaxially to the guide rod 84 b and to the guide rod 84 c respectively.

Inside the switching chamber 82 there are further obtained a first and a second opposed valve seat 81 d and 81 e, interposed between the first port 2 and the second port 3, and between the first port 2 and the third port 4 respectively. The valve seats 81 d and 81 e are suitable to be engaged reciprocatingly by the first sealing surface 83 b and by the second sealing surface 83 c of the obstructing member 83, respectively. The first port 2 is oriented orthogonally to the axis that joins the valve seats 81 d and 81 e.

In FIG. 2, the three-way valve 8 is shown in a rest position, with the circulation pump 7 in an off-state. The movable support 84 is in the intermediate or rest position, with the first sealing surface 83 b of the obstructing member 83 engaged against the first seat 81 d. Therefore, the first port 2 is in fluid communication with the third port 4, while the fluid communication between the first port 2 and the second port 3 is interrupted. As the circulation pump 7 is switched off, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is equal to the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25, which is equal to the pressure on the first port 2.

FIG. 3 shows the next operating phase, when the circulation pump 7 is switched on. The pressure produced by the circulation pump 7 at the first port 2 acts on the exposed surface of the obstructing member 83, i.e. on the second sealing surface 83 c and, since the first sealing surface 83 b is resting against the first seat 81 d, causes the overturning of the obstructing member 83 and the sealed closure of the first seat 81 d. The overturning of the obstructing member 83 drives the movable support 84 towards the first seat 81 d, against the action of the spring 85 b which compresses, and the spring 85 c which extends. As the circulation pump 7 is switched off, the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25 is greater than the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24. The arrows H in FIG. 3 show the path of the water in the three-way valve 8, while the arrow R shows the overturning of the obstructing member 83 from the position indicated with the dashed line. The system may also operate with the first sealing surface 83 b of the obstructing member 83 almost engaged against the first seat 81 d (considering the state shown in FIG. 2), i.e. with the first sealing surface 83 b of the obstructing member 83 near the first seat 81 d with the movable support 84 in the intermediate position. Turning on the circulation pump 7 will in effect tend in a first phase to bring the obstructing member 83 near to the first seat 81 d, causing the system to go through the states described above.

FIG. 4 show the third operating phase, when the circulation pump 7 is switched off again. Stopping the pump cancels the pressure difference between the two circuits, and thus the movable support 84 returns to the equilibrium position due to the return force exerted by the springs 85 b and 85 c. The movable support 84 drives with it the obstructing member 83, bringing the second sealing surface 83 c into engagement against the second seat 81 e. The obstructing member 83, having reversed its conicity in the previous operating phase, thus interrupts the fluid communication between the first port 2 and the third port 4, i.e. interrupts the circuit of the secondary exchanger 25. A fluid communication is instead established between the first port 2 and the second port 3. As the circulation pump 7 is switched off, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is equal to the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25.

FIG. 5 shows the fourth operating phase, when the circulation pump 7 is switched on again. The pressure produced by the circulation pump 7 at the first port 2 acts on the exposed surface of the obstructing member 83, i.e. on the first sealing surface 83 b and, as the second sealing surface 83 c is resting against the second seat 81 e, causes the overturning of the obstructing member 83 and the sealed closure of the second seat 81 e. The overturning of the obstructing member 83 drives the movable support 84 towards the second seat 81 e, against the action of the spring 85 c which compresses, and the spring 85 b which extends. As the circulation pump 7 is switched on, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is greater than the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25. The arrows H in FIG. 5 show the path of the water in the three-way valve 8, while the arrow R shows the overturning of the obstructing member 83 from the position indicated with the dashed line.

If the circulation pump 7 is then stopped, the pressure difference between the two circuits is canceled, and thus the movable support 84 returns to the equilibrium position due to the return force exerted by the springs 85 b and 85 c, and drives with it the obstructing members 83, returning the three-way valve 8 to the position shown in FIG. 2.

The valve described above thus operates in a cyclical manner, reciprocatingly opening and closing the heating circuit 22, 24 and the secondary heat exchanger circuit 25.

The switching on and off of the circulation pump is controlled by a control unit (not shown) of the boiler B, according to the user's demands. Sensors, e.g. pressure, temperature or flow sensors, are normally associated respectively with the heating circuit 22, 24 and the circuit of the secondary heat exchanger 25 to detect the state of operation of the two circuits. By means of these sensors, the control unit of the boiler B is thus able to determine whether the switching state of the three-way valve 8 actually corresponds to the user's demand and, if it does not, to switch the circulation pump 7 on and off again to cause a further switching of the three-way valve. This may be achieved in a short time and in any event in line with the switching times of conventional motorized valves.

Reference is now made to a second embodiment of the three-way valve, represented in FIGS. 6a -6 e.

This three-way valve 8 comprises a valve body 181, in which are obtained the first port (inlet port) 2, the second port (first outlet port) 3 and the third port (second outlet port) 4, all of which are connected to a switching chamber 182 obtained in the valve body 181.

Inside the switching chamber 182 there is arranged an obstructing member 183 that takes the form of a sliding ring, which in turn is carried by a movable support 184 made as a sliding shuttle inside the valve body 181. The direction of translation of the movable support is represented by the arrow x1 in FIG. 6a , while the direction of translation of the obstructing member 183 is represented by the arrow x2. The obstructing member 183 has a first and second sealing surface 183 b and 183 c facing away from each other (i.e. facing in opposite and divergent directions), with respect to the directions of translation x1 and x2 of the movable support 184 and of the obstructing member 183. The obstructing member 183 is mounted around a cylindrical sliding surface 184 a obtained in the middle part of the movable support 184 so that the obstructing member 183 is able to slide with respect to the movable support 184. At the opposite ends thereof, hereinafter referred to as the first and second end 184 b and 184 c, the movable support 184 has fluid passage channels 184 d, which consist of recesses with respect to the circular profile of the cross-section of the movable support 184.

Between the ends 184 b, 184 c of the movable support 184 and the respective counterparts of the valve body 181 are interposed respective opposed elastic means 185 b and 185 c, which bias the movable support 84 towards an intermediate position or equilibrium position, represented in FIG. 6a . In the example shown, the elastic means 185 b and 185 c are made as coil springs.

Inside the switching chamber 182 there are further obtained a first and a second opposed valve seat 181 d and 181 e, respectively interposed between the first port 2 and the second port 3, and between the first port 2 and the third port 4. The valve seats 181 d and 181 e are suitable to be engaged reciprocatingly by the first sealing surface 183 b and by the second sealing surface 183 c of the obstructing member 183, respectively. The first port 2 is oriented orthogonally to the axis that joins the valve seats 181 d and 181 e.

The valve in FIGS. 6a-6e has a cyclic operation similar to that of the valve in FIGS. 2-5.

In a rest position, with the circulation pump 7 in an off-state, the movable support 184 is in the intermediate or rest position, with the first sealing surface 183 b of the obstructing member 183 engaged against the first seat 181 d (FIG. 6a ). Thus, the first port 2 is in fluid communication with the third port 4, while the fluid communication between the first port 2 and the second port 3 is interrupted. As the circulation pump 7 is switched off, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is equal to the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25.

When the circulation pump 7 is switched on, the pressure produced by the circulation pump 7 at the first port 2 acts on the exposed surface of the movable support 184, i.e. on the second end 184 c of the movable support 184 and, as the first sealing surface 183 b of the obstructing member 183 is resting against the first seat 181 d, causes the sliding of the movable support 184 with respect to the obstructing member 183 towards the first seat 181 d (against the action of the spring 185 b that compresses, and of the spring 185 c that extends), and the sealed closure of the first seat 181 d by the obstructing member (FIG. 6c ). As the circulation pump 7 is switched off, the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25 is greater than the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24.

When the circulation pump 7 is again switched off, the pressure difference between the two circuits is canceled, and therefore the movable support 184 returns to the equilibrium position due to the return force exerted by the springs 185 b and 185 c. The movable support 184 drives with it the obstructing member 183, causing the second sealing surface 183 c to engage against the second seat 181 e. The obstructing member 183 thus interrupts the fluid communication between the first port 2 and the third port 4, i.e. interrupts the circuit of the secondary exchanger 25. A fluid communication is instead established between the first port 2 and the second port 3 (FIG. 6d ). As the circulation pump 7 is switched off, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is equal to the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25.

When the circulation pump 7 is switched on again, the pressure produced by the circulation pump 7 at the first port 2 acts on the exposed surface of the movable support 184, i.e. on the second end 184 b of the movable support 184 and of the obstructing member 183, i.e. on the first sealing surface 183 b and, as the second sealing surface 183 c is resting against the second seat 181 e, causes the sealed closure of the second seat 181 e. Moreover, the action of the pressure on the first end 184 b of the movable support 184 causes the movement of the movable support towards the second seat 181 e, which slides with respect to the obstructing member 183, against the action of the spring 185 c which compresses, and the spring 185 b which extends (FIG. 6e ). As the circulation pump 7 is switched on, the pressure P1 of the water at the second port 3 associated with the heating circuit 22, 24 is greater than the pressure P2 of the water at the third port 4 associated with the circuit of the secondary heat exchanger 25.

If the circulation pump 7 is then stopped, the pressure difference between the two circuits is canceled, and thus the movable support 184 returns to the equilibrium position due to the return force exerted by the springs 185 b and 185 c, and drives with it the obstructing members 183, returning the three-way valve 8 to the initial position.

FIGS. 7 to 16 show different constructive variants of the valve in FIGS. 6a and 6b . The same reference numbers have been assigned to elements corresponding to those of this valve.

FIGS. 7 and 8 show a first variant, in which the fluid passage channels 184 d at the ends 184 b and 184 c of the movable support 184 have an opening arranged completely within the circular profile of the cross-section of the movable support 184, which thus is not intersected by this opening. Note that in FIG. 7 the obstructing element 183 is not represented in an actual operating position.

FIG. 9 shows another variant, in which the elastic means are arranged inside the movable support 184. For this purpose, the movable support 184 is hollow and consists of two pieces 184′ and 184″ attached to each other. The movable support 184 is mounted in a sliding manner on a guide rod 184 e attached to the valve body 181. The elastic means 185′, in particular a single coiled spring, are mounted in a floating manner on the guide rod 184 e, so that the opposite ends 185 b′ and 185 c′ of the elastic means are able to engage reciprocatingly stops 184 f and 184 g attached on the guide rod 184 e, after the elastic means 185′ are driven by opposing shoulders 184 h and 184 i obtained inside the movable support 184.

Another characteristic of the variant of FIG. 9 is that at the opposing ends of the cylindrical sliding surface 184 a of the movable support 184 a are obtained respective stops 184 j and 184 k which are used to transfer an axial force to the obstructing member when the movable support 184 moves from the intermediate position to one or the other of the seats and also creates a higher pressure on the obstruction member 183 so that the leakage of fluid between the sealing surfaces 183 b and 183 c of the obstructing member and the valve seats 181 d and 181 e is reduced.

The variant of FIG. 10 is almost identical to that of FIG. 9, with the exception that the obstructing member 183 is mounted on an obstructing member support 183 a, which is placed in contact with the cylindrical sliding surface 184 a of the movable support 184. In this way, there is an additional degree of freedom in the design of the movable support/obstructing member group, since the material of the obstructing member support 183 a may be selected according to the desired friction characteristics with respect to the cylindrical sliding surface 184 a, without this creating any constraints with respect to the sealing characteristics of the obstructing member 183 with respect to the seats 181 d and 181 e.

FIGS. 11-13 show another variant, in which the elastic means are again arranged inside the movable support 184. For this purpose, the movable support 184 is hollow and consists of two end pieces 184′, 184″ attached to an intermediate piece 184′″. The movable support 184 is slidably mounted on a pair of opposite guide rods 184 e and 184 e′ attached to the valve body 181. The elastic means 185 b′ and 185 c′, in particular two coil springs, are each interposed between the intermediate piece 184′″ of the movable support 184 and an end of a respective guide rod 184 e and 184 e′.

The intermediate piece 184′″ of the movable support 184 bears the cylindrical sliding surface 184 a. The material of the intermediate piece 184′″ of the movable support 184 may thus be selected according to the desired friction characteristics with the obstructing member 183 or with the obstructing member support, if this is used in the variant in FIGS. 11-13.

The variant in FIGS. 14-16 is substantially similar to that of FIGS. 6a -6 b, but differs from this one in that the movable support 184 comprises two pieces 184′ and 184″ attached to each other. The cylindrical sliding surface 184 a is obtained on a liner or sleeve 184 a′ formed or mounted on one of the two pieces 184′ and 184″ of the movable support 184. The variant in FIGS. 14 and 16 also has two rings or gaskets 184 j′ and 184 k′ mounted on the movable support 184 at the opposite ends of the cylindrical sliding surface 184 a. These rings or gaskets 184 j′ and 184 k′ have a similar function to that of the stops 184 j and 184 k of the variants in FIGS. 9 and 10.

A third embodiment of the three-way valve is shown in FIGS. 17a and 17b .

This three-way valve 8 comprises a valve body 281, in which are obtained the first port (inlet port) 2, the second port (first outlet port) 3 and the third port (second outlet port) 4, all of which are connected to a switching chamber 282 located in the valve body 281. The second and third port 3, 4 are aligned with each other, while the first port 2 is oriented orthogonally to the axis connecting the second and third port.

Inside the switching chamber 282 there is arranged an S-shaped leaf 284 which, as will be clarified below, is functionally equivalent to the movable supports 84 and 184 of the preceding embodiments. The S-shaped leaf 284 has such a development because it is axially stressed between opposite ends of the switching chamber 282, arranged orthogonally to the direction of the axis connecting the second and third ports 3 and 4. A bend 283 of the S-shaped leaf forms a obstructing member similar to the obstructing members 83 and 183 of the preceding embodiments. The S-shaped leaf 284 and its bend 283 are capable of flexing reciprocatingly towards one or the other of said second and third ports 3 and 4. On the bend 283 of the S-shaped leaf 284 one may identify a first and a second sealing surface 283 b and 283 c facing away from each other (i.e. facing in opposite and divergent directions).

Inside the switching chamber 282 there are further obtained a first and a second opposed valve seat 281 d and 281 e, respectively interposed between the first port 2 and the second port 3, and between the first port 2 and the third port 4. The valve seats 281 d and 281 e are suitable to be engaged reciprocatingly by the first sealing surface 283 b and by the second sealing surface 283 c of the obstructing member/bend 283, respectively.

The obstructing member/bend 283 is capable of reversing the curvature and engaging one of the opposed seats 281 d and 281 e of the three-way valve 3, due to pressure, when the circulation pump passes from the off-state to the subsequent on-state passing through intermediate third states (symmetrical with each other) wherein, with a given curvature dictated by the switched-on configuration of the pump, with the subsequent shutdown of the pump, the leaf rests on the opposite valve seat (not shown). The next time the pump is switched on, due to the increase in pressure on the convex part of the leaf, there is a reversal of the curvature (change of concavity of the leaf) with the obstructing member/bend resting on the opposite valve seat. In other words, for its part, the leaf 284 is able to bring the obstructing member 283 into an intermediate position between the opposed seats 281 d and 281 e, due to the elastic force produced by the leaf itself, when the circulation pump goes from the on-state to the off-state.

The valve described above thus operates in a cyclical manner similar to the preceding embodiment, opening and closing the heating circuit 22, 24 and the secondary heat exchanger circuit 25 reciprocatingly.

FIGS. 17a and 17b show a single operating state with the pump switched on and fluid flowing from the port 2 to the port 4.

It is understood that the elements described in relation to only certain embodiments or variants may be combined, where compatible, with elements described in relation to other embodiments or variants. 

1. A hydraulic system for an installation for heating and generating domestic hot water, which heating installation comprises a primary heat exchanger for heating a water flow usable in a heating hydraulic circuit, a secondary heat exchanger for transferring heat from a water flow coming from the primary heat exchanger to a domestic water flow and a circulation pump for generating the water flow in the primary heat exchanger; the hydraulic system comprising a three-way valve, said three-way valve comprising a first port for connection to the primary heat exchanger, a second port and a third port for connection to the heating circuit and to the secondary heat exchanger, respectively; wherein said three-way valve is switchable between at least two positions in which the first port is selectively in fluid communication with the second port or with the third port; wherein said three-way valve comprises a movable support and an obstructing member carried by said movable support, at least one of which is responsive to pressure applied by the circulation pump at the first port, at least one of said movable support and obstructing member being movable due to transitions between an off-state and an on-state of the circulation pump; wherein the hydraulic system is characterized in that the obstructing member comprises a pair of sealing surfaces facing away from each other and adapted to engage reciprocatingly respective opposed seats of the three-way valve interposed between the first port and the second port, and between the first port and the third port, respectively.
 2. A system according to claim 1, wherein the three-way valve further comprises return means associated with the movable support and producing an elastic force to bias the movable support towards an intermediate position between the opposed seats of the three-way valve, wherein said intermediate position is associated with the off-state of the circulation pump.
 3. A system according to claim 1, wherein, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said movable support is movable towards said seat, against the action of said elastic force, due to pressure when the circulation pump switches from the off-state to the on-state.
 4. A system according to claim 3, wherein said movable support is capable of driving the obstructing member from one to the other of said opposed seats of the three-way valve due to said elastic force when the circulation pump switches from the on-state to the off-state.
 5. A system according to claim 4, wherein the movable support is slidably arranged between the opposed seats of the three-way valve and the obstructing member is formed as a flexible conical ring arranged around the movable support.
 6. A system according to claim 5, wherein, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said obstructing member is capable of overturning due to pressure when the circulation pump switches from the off-state to the on-state, as well as driving said movable support towards said seat against the action of said elastic force.
 7. A system according to claim 4, wherein the movable support is slidably arranged between the opposed seats of the three-way valve and the obstructing member is formed as a ring arranged around the movable support and slidable relative to the movable support.
 8. A system according to claim 7, wherein, when the obstructing member is engaged against one of said opposed seats of the three-way valve, said movable support is capable of moving due to pressure towards said seat and relative to the obstructing member, against the action of said elastic force, when the circulation pump switches from the off-state to the on-state.
 9. A system according to claim 3, wherein the obstructing member is carried by a S-shaped leaf axially biased to flex reciprocatingly towards one or the other of said opposed seats of the three-way valve, the obstructing member being formed as a bend of said S-shaped leaf.
 10. A system according to claim 9, wherein the obstructing member is capable of reversing curvature and engaging one of said opposed seats of the three-way valve due to pressure when the circulation pump switches from the off-state to the on-state, and wherein the S-shaped leaf is capable of bringing the obstructing member into an intermediate position between said opposed seats, due to an elastic force produced by the leaf, when the circulation pump switches from the on-state to the off-state.
 11. A system according to claim 1, wherein said three-way valve and said circulation pump are assembled into a single body. 